When Doctor Strange (Benedict Cumberbatch) begins having strange dreams that revolve around a teenage girl, he's surprised to meet her on the streets outside his ex-girlfriend Christine Palmer's (Rachel McAdams) wedding.

The girl's name is America Chavez (Xochitl Gomez), and she's being chased by a giant, slimy alien from another universe. Strange and Wong (Benedict Wong) step in and rescue her, and discover that her powers hold an important key to connecting the multiverses.

They discover that the symbols on the beast that was chasing America were runes, suggesting witchcraft — which leads Strange to search for Wanda Maximoff (Elizabeth Olsen).